Our specific objectives for the coming year concern the bioenergetics of cancer cells, particularly of mitochondrial electron transport. We propose to analyze further the stoichiometry of H ion ejection by respiring tumor mitochondria, particularly of the cytochrome oxidase reaction, using a new type of oxygen electrode and fast recording techniques we have developed, with direct data-accessing into a computer. The coupling efficiency of normal versus tumor cytochrome oxidase will be compared. We shall determine the rate and significance of H+ back-leakage in tumor mitochondria, which can determine the efficiency of energy coupling. We shall determine the H ion/ATP ratio during the breakdown and synthesis of ATP by the F0F1-ATPase activity of tumor mitochondria. With selectively permeabilized tumor cells, we propose to determine the H ion/O ratio of mitochondrial electron transport and the P/O ratio of oxidative phosphorylation in situ. We shall examine further the role of malic enzyme and its allosteric regulation in the oxidative pathway of glutamine, the major respiratory substrate of tumor cells.